1. Field of the Invention
The invention is directed to a method for manufacturing electrodes for medical applications, particularly implantable stimulation electrodes, of the type having a active layer of porous titanium nitride.
2. Description of the Prior Art
Electrodes of the above-described type are disclosed in European Patent 0 115 778. These electrodes are composed of an electrically conductive carrier material and, in the active region, have a porous layer of a carbide, a nitride or a carbonitride of at least one of the metals titanium, vanadium, zirconium, niobium, molybdenum, hafnium, tantalum or tungsten, i.e. including titanium nitride (TiN). The known electrodes are manufactured with a physical vapor deposition (PVD) process, whereby the porous layer is applied by physical vapor deposition onto the carrier material serving as a substrate. To that end, the metal that forms the carbide, nitride or carbonitride is evaporated, for example with an electron beam evaporator, from a supply of the metal in an atmosphere containing nitrogen and/or methane and the corresponding metal compound is deposited on the substrate.
The electrodes manufactured in the way set forth above are advantageously utilized as stimulation electrodes for heart pacemakers. For specific applications, however, a heart pacemaker electrode having a structured electrode arrangement is expedient, for example, wherein two conductive regions insulated from one another are arranged concentrically relative to one another. In order to achieve a high double-layer capacitance given contact with the body fluid, it is then necessary to provide the electrode with a porous titanium nitride layer. Such an electrode configuration, however, has not yet been realized with titanium nitride electrodes.